1. Field of the Invention
The present invention relates to a therapeutical apparatus of extracorporeal type, and more particularly, to a therapeutical apparatus of extracorporeal type in which an object to be treated (such as a calculus formed within a physical body of a patient) is detected by a measuring apparatus, and therapeutic shock wave energy which is generated externally of the physical body is focussed upon the object to fracture it, and specifically, to an ultrasonic therapeutical apparatus which focuses an ultrasonic shock wave from a source located externally of the physical body upon the object to be treated for the purpose of fracturing the same.
2. Prior Art
An arrangement which utilizes an X-ray or ultrasonic measuring apparatus to detect the presence of a calculus formed in a bile duct or kidney, and which also utilizes therapeutical energy in the form of a shock wave which is produced, as by voltage discharge or ultrasonic vibration, externally of the physical body of a patient and is focussed upon the calculus to fracture it, is disclosed in U.S. Pat. No. 4,617,931. As disclosed in this patent, a probe with piezoelectric elements disposed in an array in a mosaic pattern along a quadratic surface is brought into contact with a patient's back via a water bag filled with an ultrasonic wave transmitting medium such as water interposed therebetween to focus an ultrasonic shock wave from the piezoelectric elements upon a calculus, as formed within a kidney, to fracture it. As disclosed in Japanese Laid-Open patent applications No. 31,140/1988 and No. 45,747/1986, an ultrasonic probe may move across an extensive area and focus an ultrasonic wave of increased intensity upon a calculus once it is located. Japanese Laid-Open patent application No. 37,149/1986 discloses a measuring apparatus including a detection system which determines positions in two directions. The present applicant has also proposed an arrangement which permits displacement of the ultrasonic probe in a direction perpendicular to the scan direction, as disclosed in Japanese patent application No. 282,979/1986. U.S. Pat. No. 4,526,168 discloses a technique for focussing an ultrasonic wave upon a calculus by changing the timing and phases with which a plurality of piezoelectric elements are driven. In the ultrasonic therapeutical apparatus disclosed in U.S. Pat. No. 4,617,931, the ultrasonic probe is located only at the center of an ultrasonic wave generator which provides an ultrasonic wave of an increased intensity, resulting in a limited scanning field over which an observation is possible. However, such an arrangement may fail to locate a calculus. When displacement of the probe in a direction perpendicular to the scan direction is enabled as disclosed in Japanese patent application No. 282,979/1986, tracking the movement of the calculus is possible, but it is still difficult to locate the calculus before the therapy is conducted. A manual focussing operation results in a low hit rate of the ultrasonic wave whenever the calculus happens to move as a result of breathing.
The ultrasonic therapeutical apparatus disclosed in Japanese Laid-Open patent application No. 31,140/1986 enables the extent of observation to be increased, but involves a combination with a patient suspension system with the patient suspended in a bath in a water vessel, thus disadvantageously requiring a very bulky arrangement. The ultrasonic therapeutical apparatus disclosed in Japanese Laid-Open patent application No. 37,149/1986 uses X-ray in its detector, which may be hazardous to the patient. In addition, where a pair of ultrasonic probes are employed, they are located such that each scan plane passes through the focus of a reflector of the shock wave and such that their axes are perpendicular to each other. This limits the extent of observation which is available, and thus still leaves much to be improved.
The apparatus disclosed in U.S. Pat. No. 4,617,931 includes means for focussing a shock wave on a calculus. Specifically, an ultrasonic wave or X-ray is employed to detect the spatial location of a calculus within the physical body of a patient, as illustrated in FIG. 46, where the focal point of the shock wave is indicated by a marker on an image 300 which is obtained by ultrasonic or X-ray tomography. The positioning is achieved by bringing an image 302 of a calculus into alignment with the marker. Thus, the position of a focus F is indicated as shown at 304 on a display 303, and the means for generating a shock wave is moved so that the image 302 of the calculus is aligned with the position of the focus F. However, such technique only indicates the focal point of the display.
Accordingly, where organs such as lungs, intestines or bones, which are sensitive to the shock wave, are located around the calculus when the latter is to be fractured, there arises a significant problem inasmuch as such organ may be damaged or otherwise adversely influenced by the shock wave.
Another form of therapeutical apparatus of extracorporeal type is disclosed in Japanese patent application No. 282,980/1986 (see FIGS. 44 and 45). The apparatus includes ultrasonic measuring means 311 (location detecting means) which detects the location of a calculus within the physical body, positioning signal generating means 312, focus shifting means 313 and shock wave generating means 314 which generates a shock wave used to fracture a calculus.
The ultrasonic measuring means 311 includes an ultrasonic measuring unit 317 which radiates an ultrasonic wave toward a patient 315 to detect the location of a calculus 316, and a display unit 318 which receives a detection signal to indicate the location of the calculus on a CRT screen.
The positioning signal generating means 312 includes a single generator 320 which fixes a marker on a given point on the screen of the display unit 318 and produces a signal which is delivered to focus shifting means 313 which is effective to bring the focus of the fracturing shock wave into alignment with the marker. The generator 320 is effective to process the image of the detected calculus so that an operator (such as a surgeon) can recognize the size or the number of calculus or calculi displayed and to indicate a most effective signal on the screen as by a light pen to indicate the sequence in which the calculi are to be fractured in order of decreasing size, or to indicate a particular region of a coral calculus where the fracture is to be initiated or to change the focal point of the shock wave in response to the location and size of the calculus which is performed periodically during the fracturing process because of a displacement of the calculus. The generator stores such signals, and delivers them to a drive unit 319 which shifts the shock wave generator during the fracturing process.
The focus shifting means 319 or the drive unit which shifts the shock wave generator operates to drive both a water bag 321 and a shock wave generator 322 by means of a numerically controlled robot in accordance with the positioning signal. The shock wave generator 322 includes a plurality of ultrasonic vibrators or piezoelectric elements 323 which are applied to and secured to the front surface of a mounting plate 324, which is formed as a spherical surface, in a mosaic pattern. The front surface of the piezoelectric elements which emit the shock wave is directed toward the patient 315. The water bag 321 includes an ultrasonic wave transmitting medium and means for injecting liquid medium and controlling the pressure of the medium.
The water bag is interposed between the shock wave generator 322 and the patient 315. The shock wave transmitting liquid (such as water) fills the bag 321.
The shock wave generating means 314 includes a known ultrasonic pulse voltage generator for driving the piezoelectric elements 323.
FIG. 45 indicates the sequence of operation performed by the apparatus mentioned above. Initially, the location of the calculus within the physical body of a patient is determined by the measuring means 311. The positioning signal generating means 312 analyses the condition of the calculus which is detected by the measuring means. An operator (such as a surgeon) selects an optimum procedure to treat the calculus depending on the kind thereof. In response thereto, a positioning signal (which determines the sequence of treatment) is stored. The focus shifting means 313 is activated in accordance with the positioning signal to drive the water bag 321 and the shock wave generator 322 so that the shock wave is focussed upon the calculus. Subsequently, a shock wave is generated in response to the shock wave generating means 314 to fracture the calculus. After a given number of shock waves have been generated, the procedure is temporarily stopped, and the size of the remaining calculus or the focal point of the shock wave is determined again, and the above operation is repeated until the calculus is completely fractured.
However, in the therapeutical apparatus of extracorporeal type as mentioned above, the use of the ultrasonic wave for observing the location of a calculus and for aiming fails to provide a tomographic image of good quality because of the spacing between the apparatus and the patient. This makes it difficult to aim the apparatus.
In addition, in the apparatus described above, the entire shock wave generator has been moved in order to bring the focal point of the shock wave into alignment with the calculus. However, because the shock wave generator (including the water bag) is of an increased weight, an extensive unit is required for such movement and the apparatus lacks speed.
On the other hand, a calculus or tumor which is to be treated by such an apparatus tends to move in response to breathing or movement of blood vessel, and thus may be displaced from the focal point of the ultrasonic beam. In such instance, the focal point of the ultrasonic beam must be aligned with a region to be treated to avoid wasteful generation of an ultrasonic wave. This increases the length of time required for the therapy and also jeopardizes normal tissues. Movement caused by breathing may be rapid enough to prevent automatic tracking of the focal point of the ultrasonic beam on the moving calculus since the water bag itself has a given magnitude.
Almost all apparatus of the kind described utilize a devoted bed on which a patient is positioned in a supine posture. The bed includes a table section supporting an upper region of a patient including his shoulder and head and another table section supporting a lower section extending from the waist to the feet, leaving a free space between the breast and the abdomen. A patient is laid in a supine posture on the bed, and the measuring apparatus as well as a unit for generating therapeutical energy are brought close to or into abutment against the patient to perform the treatment. Accordingly, the patient has a small degree of freedom during the therapy, which restricts the space requirement for the measuring apparatus and the energy generating apparatus. Specifically, with an X-ray measuring apparatus, it is only possible to cause the X-ray to transmit through the physical body of a patient. With an ultrasonic measuring apparatus, it is only possible to move the ultrasonic vibrator along the surface of the physical body.
There has been no capability to provide an efficient, fine adjustment of the angle with which the X-ray transmits or the angle at which the ultrasonic wave is emitted. It has been impossible to locate a shock wave generator at an angle which avoids the lung when treating a biliary calculus or to adjust the angle at which the shock wave is emitted to an efficient angle. It has only been possible to guide the shock wave generator along the physical body of a patient.
Usually, a supine posture is chosen for therapy of a biliary calculus while either a supine or prone posture is chosen for treating a renal calculus, and it is unfavorable that a posture used for the therapy be restricted by a devoted bed.
Hospitals usually have an X-ray apparatus and an ultrasonic diagnostic apparatus, and therefore it is uneconomical for the hospital to purchase a separate extracorporeal therapeutical apparatus with a devoted bed. It is desirable that a therapeutical apparatus of extracorporeal type be provided which uses a common bed which allows a free choice of either supine or prone posture.
Thus, an ordinary hospital is usually provided with an X-ray unit or ultrasonic diagnostic apparatus which may be used as the measuring apparatus mentioned above as well as associated patient beds. If an extracorporeal therapeutical apparatus as mentioned above must be provided anew, an increased demand in space requirement and additional cost result.